牧草大鎌の研究 (第2報)
国産大鎌とオーストリア製大鎌の刃部の比較
1967 年 29 巻 1 号 p. 26-32
詳細
1967 年 29 巻 1 号 p. 26-32
The auther compared a Japanese scythe blade with an Austrian one on the following articles; the shape, the metallurgical structure, the chemical components, the distribution of hardness, the breakage by impact, and so on. The results are as follows.
(1) The carbon content of the Austrian one was 0.75%. That of the Japanese was 1.2-1.4% in the high carbon layer and was 0.15% in the low carbon layer.
(2) The overall length of the Austrian blade was 60cm and that of the Japanese was 45cm. However the weight of the Austrian blade (400g) was lighter than that of the Japanese (430g), for the reason that the thickness of the former (0.7-0.8mm) was less than that of the latter (1.0-1.2mm).
(3) The shape of the Austrian scythe edge was formed from the two curved surfaces because of “hammering” and its wedge angle was about 10 degrees. While that of the Japanese was formed from two planes and its wedge angle was about 15 degrees.
(4) According to the microscopic examination, the metallurgical structure of the Austrian scythe blade consisted chiefly of troostite and granular ferrite and at the part of the edge point the flow of the structure by “hammering” was observed. The structure of the Japanese one was divided into two parts; the one (a high carrion layer) consisted of granular cementite, troostie and martensite, and the other a low carbon layer consisted of ferrite and fine pearlite.
(5) By the micro Vickars hardness tester, the hardness of the Austrian blade was about Hv550 and that of the edge point was about Hv690. The hardness of the Japanese was about Hv850 at the high carbon layer and was about Hv190 at the low carbon layer.
(6) By the impact, the edge of the Austrian scythe blade was not broken but deformed, while the edge of the. Japanese was broken off because of too hard.
As a result, it can be said that there is the wide difference between the Japanese scythe blade and the Austrian one. The Austrian scythe blade is made of a homogeneous layer of steel, while the Japanese one is consisted of two welded layers (a two carbon steel and a high carbon steel). In the case of edge-giving, the former is hammered and whetted; the latter is whetted only.
